We request funds for a Thermo Fisher Scientific Orbitrap Fusion mass spectrometer with ETD (Electron Transfer Dissociation) to be housed in the proteomics core of the UC Davis Genome center. The core facility is the sole resource in the area and performs a large number of proteomic analyses. However, the needs of many researchers in the areas of post-translational modifications, quantitation, and top-down analyses are currently not being met with existing instrumentation. The Thermo Scientific Fusion ETD is a next generation state-of-the-art hybrid mass spectrometer that has several unique characteristics that will enable the proteomics core to characterize endogenous post-translational modification including phosphorylation, glycosylation, and chemical modifications with cross-linking agents. It will also enable the comprehensive structural elucidation of large macropeptides and proteins. It will further enhance our capabilities for quantitating proteins. There is currently an unmet demand by the core group of NIH funded investigators for proteomic analyses that includes quantitative proteomic profiling, site-specific analysis of endogenous post-translational modifications such phosphorylation and O- and N-linked glycosylation, and chemical modification such as in cross linking experiments. There is a need for de novo sequencing of large macropeptides with extensive post translational modifications. The Orbitrap Fusion ETD is expected to have an immediate and a major impact on the research efforts of the major users listed in this proposal and the greater UC Davis research community and the nascent biotechnology start-ups clustered in the areas. This mass spectrometer will be integrated into our core facility and its existing infrastructure will integrate the operation, maintenance and management of this instrument.